Device for recognising containers

ABSTRACT

A device for recognising a container by means of a marking provided on its surface, comprising a camera and light emission means ( 1, 2, 3 ) arranged for imaging the marking ( 4 ) on the container ( 5 ). The means is connected to a processor adapted for recognition, based on a camera-recorded image of the marking, of distinctive features related to the container. To ensure that the image has the quality required for recognition of the container, the means consists of one camera ( 1 ) and two light sources ( 2, 3 ), the said light sources being positioned in such manner, either on the same or on each side of the camera, that light emitted from the respective light sources falls in from a different direction relative to the marking, thereby allowing the camera to take two images of the marking using light emitted successively from the respective light source. Alternatively, the means may consists of two cameras and one light source, the cameras being positioned in such manner, either on the same or on each side of the light source, that the optical axis of the respective camera falls in from a different direction relative to the marking, so that the cameras can take two images of the marking simultaneously. In yet another alternative, just one camera and one light source are used, wherein the camera is pointed towards an assembly of mirror faces which in pairs are positioned relative to one another in such manner that the camera is able simultaneously to take two mirror images from different directions in the mirror faces adjacent to the optical axis of the camera.

The present invention relates to a device for recognising a container,and in particular to a device for recognising distinctive featuresrelated to the container by means of a camera-recorded image of amarking provided on its surface.

There are a number of different types of devices for recognising acontainer based on various distinctive features related to the containersuch as its shape, bar code and material, especially in connection withreverse vending machines for beverage containers. In general, suchdevices function satisfactorily, provided that the container has theexpected property, thereby allowing non-returnable containers to berejected. However, practice shows that this is not sufficient to preventnon-returnable containers from being accepted during the recognitionprocess, as it is possible to beat systems of this type, for example, byattaching a bogus bar code to the container.

In view of this, it has therefore been suggested, as an additionalprecaution, that each container should be provided with an extra markingin the form of one or more surface irregularities which extend outwardsor inwards, and which mean that the surface of the container is not flatin the area of the marking. Recognition of containers that are marked inthis way can be effected, as taught in U.S. Pat. No. 5,693,017, by usinga camera-recorded image of the marking, i.e., using a camera and lightemission means that is directed towards the embossment, and which isconnected to a processor suitably equipped for recognition of thecontainer.

Normally the containers are made by cold processing aluminium, forexample, by rolling the end face with the pouring opening and deepdrawing the actual container body. Such cold processing, by both rollingand deep drawing, results in the formation of minute flaws in thesurface of the aluminium parallel to the rolling or drawing direction.These flaws have not caused any disadvantages in connection withconventional container recognition, but it has been found, however, thatthey cause unexpected problems during camera-recorded imaging of themarking on the container surface. More specifically, the problemconcerned consists of specular reflection along the length of the flawsand diffuse reflection transverse to the flaws. The consequence of thesereflections is that the image often does not have the quality, i.e. thesharpness, that the processor requires for container recognition.Moreover, tests have confirmed that the problem is just as great nomatter how far the marking extends from the container surface.Consequently, an undesirably large number of the containers are rejectedduring the recognition process as a result of the flaws caused by thecold processing.

Accordingly, the object of the present invention is to eliminate theproblems mentioned above in connection with the flaws in the containersurface, and thus provide a device for recognising a container, in whichthe image has the quality required for reliable recognition of thecontainer with a minimum of rejections.

According to one aspect, the present invention provides a device forrecognising a container by means of a marking provided on its surface,comprising a camera and light emission means arranged for imaging themarking on the container, wherein the camera and light emission means isconnected to a processor or the like adapted for recognition, based on acamera-recorded image of the marking, of distinctive features related tothe container, and wherein the camera and light emission means faces themarking during the imaging process, characterised in that the camera andlight emission means consists of one camera and at least two lightsources, said light sources being positioned in such manner, either onthe same side or on each side of the camera, that light emitted by therespective light sources falls in from a different direction relative tothe marking, and that the camera and light emission means is controlledin such manner by the processor that the camera can take at least twoimages of the marking using the light emitted successively from therespective light source or the selectively chosen light source group.

Thus, the camera can take at least two images using light that falls infrom a different direction relative to the markings, so that at leastone of these images has the image quality required for recognition ofthe container.

According to a second aspect, the present invention provides a devicefor recognising a container by means of a marking provided on itssurface, comprising a camera and light emission means arranged forimaging the marking on the container, wherein the camera and lightemission means is connected to a processor or the like adapted forrecognition, based on a camera-recorded image of the marking, ofdistinctive features related to the container, and wherein the cameraand light emission means faces the marking during the imaging process,characterised in that the camera and light emission means consists of atleast two cameras and one light source, said cameras being positioned insuch manner, either on the same side or on each side of the lightsource, that the optical axis of the respective camera falls in adifferent direction relative to the marking, and that the camera andlight emission means is controlled in such manner by the processor thatthe cameras or the selectively chosen camera group can take at least twoimages of the marking simultaneously.

Thus, the camera can take at least two images simultaneously with therespective optical axis falling in a different direction relative to themarking so that at least one of these has the image quality that assuresrecognition of the container. The operating speed is also increasedsince the images are taken simultaneously by the cameras.

According to yet another aspect, the present invention provides a devicefor recognising a container by means of a marking provided on itssurface, comprising a camera and light emission means consisting of onecamera and at least one light source, and which is arranged for imagingthe marking on the container, wherein the camera and light emissionmeans is connected to a processor or the like adapted for recognition,based on a camera-recorded image, of distinctive features related to thecontainer, characterised by an assembly of mirror faces which in pairsare positioned relative to one another in such manner that the cameracan take two images of the marking simultaneously, the said mirror facesin respective pairs being positioned on the same side of the opticalaxis of the camera and facing each other, with one of the mirror facesadjacent to the optical axis, and that the camera during the imagingprocess is pointed towards the mirror faces adjacent to the opticalaxis, in which the marking is shown as two mirror images seen fromdifferent directions.

Thus, the camera is able simultaneously to take two images of themarking seen from different directions, which images consist of themirror images of the markings that are shown on the mirror facesadjacent to the optical axis of the camera. In addition, only one camerais required and the operating speed is reduced as a result of thesimultaneous imaging.

Other advantageous features and aspects of the present invention will beunderstood from the dependent claims and the description.

The invention will now be explained in more detail with reference to theattached drawings and with the aid of exemplary embodiments, in whichthe present device is an integral part of a reverse vending machine forbeverage containers.

FIG. 1 a is a schematic perspective view of an embodiment of the presentdevice arranged in connection with the conveyor of a reverse vendingmachine, comprising a camera and light emission means consisting of onecamera and two light sources placed on either side of the camera,wherein means is arranged for imaging a marking provided in the end faceof the container and is controlled in such manner by a processor thatthe camera can image the marking using light successively emitted fromthe light sources.

FIG. 1 b is a schematic perspective view of a second embodiment of thepresent device corresponding to FIG. 1 a, except that the marking isprovided on the side face of the container and the two light sources areplaced on the same side of the camera.

FIG. 2 a is a schematic perspective view of yet another embodiment ofthe present device corresponding to FIG. 1 a, except that the camera andlight emission means consists of two cameras that are placed on the sameside of one light source and is controlled in such manner that thecameras can image the marking simultaneously.

FIG. 2 b is a schematic perspective view of still another embodiment ofthe present device corresponding to FIG. 2 a, except that the marking isprovided on the side face of the container and the two cameras areplaced on either side of the light source.

FIG. 3 is a schematic perspective view of yet another embodiment of thepresent device, in which the camera and light emission means consists ofone camera and one light source, wherein the camera is directed towardsan assembly of mirror faces which in pairs are positioned relative toone another in such manner that the camera is able simultaneously totake two images of the marking that is shown in the two mirror facesadjacent to the optical axis of the camera.

FIG. 4 a shows by means of a schematic section of an embodiment of thepresent device, in which the marking is on the end face of the containerand when one camera and two light sources are used, the three anglesformed between the two lines drawn respectively from the centre point ofthe end face to the centre point of each light source, from the centrepoint of the outer light source to the outer edges of the end face alongthe respective diameter and from the centre point of the camera lens tothe outer edges of the end face along the respective diameter.

FIG. 4 b shows by means of a schematic section of an embodiment of thepresent device, in which the marking is on the end face of the containerand when two cameras and one light source are used, the three anglesformed between the two lines drawn respectively from the centre point ofthe end face to the centre point of each camera, from the centre pointof the outer camera to the outer edges of the end face along therespective diameter and from the centre point of the light source to theouter edges of the end face along the respective diameter.

FIGS. 5 a-c show in cross section different embodiments of the mirrorfaces adjacent to the optical axis of the camera.

Although in the discussion of the drawings it is mentioned that thepresent device is a part of a reverse vending machine for beveragecontainers, it should be noted that the invention is not limited toeither reverse vending machines or to beverage containers. Consequently,the device according to the invention could be included in a structure,e.g., a sorting plant, where it is appropriate to recognise containersbased on a camera-recorded image of the marking thereon. Similarly, thecontainers may be filled with or have contained any suitable medium.

Moreover, it should be noted that known reverse vending machines may beconstructed in different ways depending upon the specificationsregarding their operation. For the sake of simplicity, the present setof figures therefore shows only the components that are necessary forthe understanding of the actual invention, i.e., the present camera and,light emission means, the mirror assembly, the associated processor withcomparator and reference archive, and the conveyor of the reversevending machine. The present device for recognising containers, based ona camera-recorded image of the marking provided on the surface of thecontainer, may thus constitute a supplementary element in a reversevending machine which has, for example, conventional equipment forrecognition by means of the shape, bar code and material of thecontainer. Such conventional recognition equipment could also in somecases be replaced by the device according to the invention.

The conveyors that are illustrated schematically in the drawings are ofany type used in such reverse vending machines, for example, of the typeable to rotate the container about its longitudinal axis into the rightposition relative to the equipment for recognition of the bar code etc.In that case, the conveyor may consist of two conveyor belts sopositioned that they form a V-shape in cross section, and which aredrawn apart to bring the container into contact with subjacent rollersfor rotation about its longitudinal axis.

The schematically illustrated processors are of any commonly used type.The processors are adapted to control the operation of the camera andlight emission means that are components of the different embodiments ofthe present device, and preferably comprise a comparator and a referencearchive. During the container recognition procedure, the processorselects the image that the comparator is to compare with the referencearchive, so that distinctive features related to the container can thusbe recognised.

As shown in FIGS. 1 a-1 b, the device for recognising containerscomprises, according to a first aspect of the invention, a camera andlight emission means 1, 2, 3 or 11, 12, 13 arranged for imaging amarking 4 or 14 provided either on the end face or the side face of thecontainer 5 or 15. This means is connected to a suitable processor orthe like and is positioned in such manner that when the container is ona conveyor 6 or 16, as shown, the marking faces it.

In order at least to produce one image of the marking that is sharpenough for use during recognition of the container by the processorequipped with the comparator and the reference archive, the meansmentioned above consists of one camera 1 or 11, and two light sources 2,3 or 12, 13 that are positioned either on each side of or on the sameside of the camera. In the embodiments shown in FIGS. 1 a-b, the lightsources are placed on either side and on the same side of the camera,respectively. Alternatively, the light sources in both these cases maybe placed (not shown) on the same side or on either side of the camera.It is also possible to use more than two light sources (not shown),which are then grouped as desired relative to the camera, so that morethan two images of the marking can be taken, if so desired.

According to a second aspect of the present invention, the camera andlight emission means, as shown in FIGS. 2 a-b, has two cameras 31, 32 or41, 42 placed on the same side or on each side of one light source 33 or43. It is also possible to use more than two cameras (not shown), whichare grouped as desired relative to the light source, so that more thantwo images can be taken as required. In this case, the processor iscontrolled in such manner by the processor that the marking 34 or 44 isimaged simultaneously by the cameras, or selectively chosen groups ifmore than two cameras are used, i.e., the light source can emit lightthat is synchronised with a respective camera or group of cameras. Inthe respective cases, unlike the embodiments shown in FIGS. 2 a-b, thecameras may be placed on the same side or on each side of the lightsource (not shown).

As shown in FIGS. 1 a-b, the camera 1 or 11 is preferably positionedabove the conveyor 6 or 16, with the camera positioned in such mannerthat the optical axis falls essentially perpendicular to the marking 4or 14. Similarly, the light source 33 or 43, as shown in FIGS. 2 a-b, ispreferably positioned above the conveyor 36 or 46, with the light sourcepositioned in such manner that emitted light falls essentiallyperpendicular to the marking 34 or 44.

If using, as shown in FIG. 4 a, a marking on the end face 7 of thecontainer and light sources 2, 3 positioned on the same side of thecamera 1, the interpositioning should be such that fulfils theexpression:α≧β+γ, wherein

-   -   α is the angle between the two lines drawn from the centre point        of the end face of the container to the centre point of each        light source;    -   β is the angle between the two lines drawn from the centre point        of the outer light source to the outer edges of the end face of        the container along the respective diameter; and    -   γ is the angle between the two lines drawn from the centre point        of the camera lens to each outer edge of the end face of the        container along the respective diameter.

When using a marking on the end face 37 of the container and two cameras31, 32 placed on the same side of the light source, theinterpositioning, as shown in FIG. 4 b, ought to be such that it fulfilsthe expression:α≧β+γ, wherein

-   -   α is the angle between the two lines drawn from the centre point        of the end face of the container to the centre point of each        camera;    -   β is the angle between the two lines drawn from the centre point        of the outer camera lens to the outer edges of the end face of        the container along the respective diameter; and    -   γ is the angle between the two lines drawn from the centre point        of the light source to each outer edge of the end face of the        container along the respective diameter.

The camera and light emission means is in accordance with a third aspectof the invention limited to just one camera 62 and at least one lightsource 63. However, as shown in FIG. 3, it is required that an assemblyof mirror faces 67, 68, 69, 70 be used, which in pairs are positionedrelative to each other in such manner that the camera can simultaneouslytake two images of the marking 64 on the surface of the container 65,and also that the mirror faces in respective pairs are placed on thesame side of the optical axis of the camera and facing each other, withone of the mirror faces 67, 68 adjacent to the optical axis. Thus, thesimultaneous imaging consists of the two mirror images of the markingthat are shown on the mirror faces adjacent to the optical axis, andwhich are seen from different directions.

In this case, the camera 62 is directed towards the mirror facesadjacent to the optical axis. The light source 63, however, is directedtowards the marking 64 on the surface of the container 65, and may beplaced on the desired side of the camera. FIG. 3 shows the use of asingle light source which covers the whole marking. However, it will beunderstood that several light sources having, for example, differentlight intensity, can be used, and that the positioning can differ fromthat shown. If, unlike the embodiment shown in FIG. 3, the marking islocated on the side face of the container, the assembly of mirror faces67, 68, 69, 70 must be placed longitudinally relative to thelongitudinal axis of the container, with corresponding relocation of thecamera and the light source.

The size of the mirror faces 67, 68, 69 and 70 in the respective pairsdepends upon the distance between the marking 64 and the camera 62, andmust be selected so that the whole field of view is covered. The angularposition of the mirror faces relative to each other in the respectivepairs is determined by the level at which the mirror faces are placedrelative to the marking 64. Furthermore, the mirror faces 67, 68adjacent to the optical axis of the camera are symmetrically placed andface in the opposite direction to each other. Preferably, the line ofintersection between the mirror faces 67, 68 adjacent to the opticalaxis of the camera is essentially at right angles to the optical axisand is parallel to the end face bearing the marking 64. This is not acondition for the mirrors as such, as it will be appreciated that thesemust be angled in a desired manner in order to enable the camera toimage the marking with the aid of the mirror face pairs.

Preferred embodiments of the mirror faces 67, 68 adjacent to the opticalaxis of the camera are shown in FIGS. 5 a-c. Thus, the mirror faces mayconsist of a triangular prism body, of which the two sides facing thecamera are mirror-coated, or of two square, mirror-coated plates. In thelast-mentioned case, the side edge of the plates adjacent to the opticalaxis is bevelled, and is either positioned so that the two bevelled sideedges meet or has the plates offset relative to each other along theoptical axis. With an embodiment of the mirror faces adjacent to theoptical axis as shown in FIGS. 5 a-b, the centre point of the mirrorfaces will lie substantially along a straight line. However, in theembodiment shown in FIG. 5 c, the centre point of the mirror faces inthe respective pairs will lie along respective straight lines that areparallel to each other.

The marking on the container may have any suitable design. Typicalexamples are lo embossed patterns, impressed patterns, ridges etcextending outwards or inwards relative to the container surface, barcodes, texts, symbols, Braille and colouring agents applied externallyon the container.

The light emitted by the respective light sources is of any suitabletype, preferably short-pulsed light. The light sources may consist of atleast one light-emitting diode. It should also be added that the camerasmentioned above are of any type within this field, for example, a CCDcamera.

1. A device for recognising a container by means of a marking providedon its surface, comprising a camera and light emission means (1, 2, 3;11, 12, 13) arranged for imaging the marking (4; 14) on the container(5; 15), said camera and light emission means being connected to aprocessor or the like adapted for recognition, based on acamera-recorded image of the marking, of distinctive features related tothe container, and wherein the camera and light emission means faces themarking during the imaging process, where the camera and light emissionmeans comprise one camera (1; 11) and at least two light sources (2, 3;12, 13), the light sources being positioned in such manner, either onthe same or on each side of the camera, that light emitted from therespective light source falls in from a different direction relative tothe marking, and that the camera and light emission means is socontrolled by the processor that the camera can take at least two imagesof the marking using light emitted successively from the respectivelight source or the selectively chosen light source group, said devicebeing characterized in that when the marking (4) is provided in an endface of the container (5), then the camera (1) and the light sources (2,3) are interpositioned so as to fulfil the expression:α≧β+γ, wherein α is the angle between the two lines drawn from thecentre point of the end face on of the container to the centre point ofeach light source; β is the angle between the line drawn from the centrepoint of the outer light source to the outer edges of the end faces ofthe container along the respective diameter; and γ is the angle betweenthe two lines drawn from the centre point of the camera lens to eachouter edge of the container along the respective diameter.
 2. A devicefor recognising a container by means of a marking provided on itssurface, comprising a camera and light emission means (31, 32, 33; 41,42, 43) arranged for imaging the marking (34; 44) on the container (35;45), said camera and light emission means being connected to a processoror the like adapted for recognition, based on a camera-recorded image ofthe marking, of distinctive features related to the container, andwherein the camera and light emission means faces the marking during theimaging process, where the camera and light emission means consists ofat least two cameras (31, 32; 41, 42) and one light source (33; 43), thecameras being positioned in such manner, either on the same or on eachside of the light source, that the optical axis of the respective camerafalls in from a different direction relative to the marking, and thatthe camera and light emission means is so controlled by the processorthat the cameras or the selectively chosen camera group can take atleast two images of the marking simultaneously, said device beingcharacterised in that when the marking (34) is provided in an end faceof the container (35), the cameras (31, 32) and the light source (33)are interpositioned so as to fulfil the expression:α≧β+γ, wherein α is the angle between the two lines drawn from thecentre point of the end face of the container to the centre point ofeach camera; β is the angle between the line drawn from the centre pointof the outer camera lens to the outer edges of the end face of thecontainer along the respective diameter; and γ is the angle between thetwo lines drawn from the centre point of the light source to each outeredge of the container along the respective diameter.
 3. A device forrecognising a container by means of a marking provided on its surface,comprising a camera and light emission means consisting of one camera(62) and at least one light source (63), and which is arranged forimaging the marking (64) on the container (65), said 5 camera and lightemission means being connected to a processor or the like adapted forrecognition, based on a camera-recorded image of the marking, ofdistinctive features related to the container, characterised by at leasta first pair (67, 69) and a second pair (68, 70) of mirrors, where themirrors in each pair are facing one another and where the pairs are 10positioned on opposite sides of the optical axis of said camera (62),one mirror (67) of the first pair being fixedly positioned adjacent toone mirror (68) of the second pair, at an angle to said axis, wherebythe marking is shown as two mirror images seen from different directionsand the camera is able to take two images of the marking (64)simultaneously.
 4. A device according to claim 1, characterised in thatthe camera (1; 11), or the light source (33; 43) is placed at a levelabove the container (5; 15; 35; 45).
 5. A device according to claim 1,characterised in that the respective light sources (2, 3) emit lightthat is synchronised with the exposures of the camera (1).
 6. A deviceaccording to claim 2, characterised in that the light source (33) emitslight that is synchronised with the exposure of the respective cameras(31, 32).
 7. A device according to claim 1, characterised in that thelight is short-pulsed light.
 8. A device according to claim 1,characterised in that the light source (2, 3; 33) consists of at leastone light-emitting diode.
 9. A device according to claim 3,characterised in that the line of intersection between the mirror faces(67, 68) adjacent to the optical axis of the camera is essentiallyperpendicular to the optical axis, these mirror faces beingsymmetrically positioned and directed in the opposite direction to eachother.
 10. A device according to claim 9, characterised in that themirror faces adjacent to the optical axis of the camera are sopositioned that one of their sides edges meet.
 11. A device according toclaim 9, characterised in that the mirror faces adjacent to the opticalaxis of the camera are offset relative to each other along the opticalaxis.
 12. A device according to claim 1, characterised in that theimaging is performed when the container (5; 35; 65) is on a conveyor (6;36; 66) installed in a reverse vending machine for beverage containers.13. A device according to claim 1, characterised in that the processorcomprises a comparator designed for recognition, based on the imageselected by the processor, of the marking on the container (5; 35; 65)by comparing with a reference archive of markings and thus recognisingdistinctive features related to the container.
 14. A device according toclaim 2, characterised in that the camera (1; 11), or the light source(33; 43) is placed at a level above the container (5; 15; 35; 45).
 15. Adevice according to claim 2, characterised in that the light isshort-pulsed light.
 16. A device according to claim 3, characterised inthat the light is short-pulsed light.
 17. A device according to claim 2,characterised in that the light source (2, 3; 33) consists of at leastone light-emitting diode.
 18. A device according to claim 3,characterised in that the light source (2, 3; 33) consists of at leastone light-emitting diode.
 19. A device according to claim 2,characterised in that the imaging is performed when the container (5;35; 65) is on a conveyor (6; 36; 66) installed in a reverse vendingmachine for beverage containers.
 20. A device according to claim 3,characterised in that the imaging is performed when the container (5;35; 65) is on a conveyor (6; 36; 66) installed in a reverse vendingmachine for beverage containers.
 21. A device according to claim 2,characterised in that the processor comprises a comparator designed forrecognition, based on the image selected by the processor, of themarking on the container (5; 35; 65) by comparing with a referencearchive of markings and thus recognising distinctive features related tothe container.
 22. A device according to claim 3, characterised in thatthe processor comprises a comparator designed for recognition, based onthe image selected by the processor, of the marking on the container (5;35; 65) by comparing with a reference archive of markings and thusrecognising distinctive features related to the container.